1. Field of the Invention
The present invention relates to a paging apparatus having a message memory function.
2. Description of the Related Art
In recent years, as a new paging system, a system which calls a certain paging apparatus and can transfer a message from a base station to display it on the paging signal transmitted from a base station is received and demodulated by a receiving circuit of an apparatus, and the demodulated signal is input to a control circuit. The control circuit collates an ID code included in the received paging signal with the ID code prestored in an ID-ROM disposed in the paging apparatus. Upon collation, if two codes coincide with each other, the control circuit supplies a ringing signal to a loudspeaker via a driver. For this reason, the loudspeaker generates a ringing tone, and it is signaled to a user whose apparatus is paged. When the two ID codes coincide with each other, the control circuit decodes a message code included in the received paging signal together with the ID code, and causes a liquid crystal display to display the decoded message.
The apparatus of this type comprises a message memory, and the received message code is stored in the message memory. For this reason, after a display of the received message is turned off, the received message can be read out from the message memory as needed, and can be redisplayed on the liquid crystal display. However, the number of messages to be stored in the message memory is limited. Thus, when a new message code is received while the memory is full, the oldest message code is cleared, and the new message code is stored.
The paging apparatus having the message memory has, e.g., a "preservation mode" and a "clear mode" in addition to a "display mode" as control modes associated with message code control. In the preservation mode, when a new message is received while the memory is full, the already stored message codes are prevented from being cleared. In the clear mode, when a message code stored in the memory becomes unnecessary, the message code is cleared. These "preservation" and "clear" modes are executed by the following operations as well as the "display mode".
More specifically, the paging apparatus comprises three, i.e., first to third message control switches. When the "display mode" is to be executed, the first switch is depressed, and the paging apparatus is set in the display mode. Thus, of a plurality of message codes stored in the message memory, the latest message code, for example, is read out, is decoded by a CPU, and is displayed on the liquid crystal display. In this state, when the second switch is depressed once, the second latest message code is read out from the message memory, and is displayed on the liquid crystal display after the code is decoded. Thereafter, every time the second switch is depressed once, the message codes are read out from the message memory one by one from the new one, and are displayed on the liquid crystal display in turn.
In the "preservation mode", a message to be preserved is read out from the message memory, and is displayed on the liquid crystal display upon operation in the "display mode". In this state, the third switch is depressed once, and the paging apparatus is set in the preservation mode. Thereafter, the first switch is depressed. Thus, the message displayed on the liquid crystal display is protected from being naturally cleared upon reception of a new message code, and is then stored in the message memory in the protected state.
In the "clear mode", a message to be cleared is read out from the message memory and is displayed on the liquid crystal display upon operation in the "display the third switch is successively depressed twice, and the paging apparatus is set in the clear mode. Thereafter, the first switch is depressed. Thus, the message displayed on the liquid crystal display is cleared from the message memory.
In the above-mentioned system, however, three switches are required to execute the message display, preservation, and clear modes. For this reason, the apparatus becomes bulky, and this undesirably causes a decrease in reliability and an increase in cost.